It is well known that automobile engines tend to form deposits on the surface of engine components, such as carburetor ports, throttle bodies, fuel injectors, intake ports and intake valves, due to the oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile's fuel consumption. Increased production of exhaust pollutants also occurs. For these reasons, fuel detergents or "deposit control" additives have been developed to minimize or prevent such deposits.
Deposit control additives, however, differ in their effectiveness for preventing or controlling deposits on various engine components. Effectiveness differences occur because engine components operate at different temperatures. Some deposit control additives are not sufficiently stable on the surface of certain engine components to perform their intended function. In this regard, deposits on intake valves are particularly difficult to control as intake valve operating temperatures can exceed 300 degrees C. At these temperatures, many fuel additives are too volatile to be effective, while others thermally decompose.
Therefore, what is needed is an effective deposit control additive which has improved thermal stability at normal engine intake valve operating temperatures which also possess sufficient molecular weight so as to be nonvolatile at these temperatures.